The present invention relates to an expansible plug for anchoring in a drilled hole having an undercut, consisting of a threaded bolt and an expansible sleeve.
Expansible plugs of the above mentioned general type are known in the art. DE 31 24 685 C2 discloses an expansible plug which consists of a threaded bolt having an expander cone at its leading end, and an expansible sleeve which has longitudinal slits starting from its leading end and extending for a part of its length. To anchor the expansible plug in a drilled hole having an undercut at the bottom thereof, the expansible sleeve is driven onto the expander cone of the threaded bolt which bears against the bottom of the drilled hole. During this process, the expansible segments of the expansible sleeve that are created by the longitudinal slits are bent into the undercut. The result is therefore an interlocking anchorage, which, by virtue of the expansible segments bent into the undercut, is able to compensate for any enlargement of the drilled hole as a result of cracks forming. The known expansible plug is then used in particular in the case of anchorings in the tensile zone in which cracks commonly form.
The known expansible plugs possess some disadvantages.
The function of the known expansible plug is impaired, however, if dynamic loads act on the plug or the anchoring substrate is subjected to dynamic loads. Because the plug and the anchoring substrate are being constantly subjected to stress and relieved of stress, the cracks close and open, so that as a consequence of the constant change in the expansion pressure exerted by the wall of the drilled hole on the expansible sleeve, the wall of the drilled hole is gradually reamed out in the anchoring region by the hard expansible sleeve which consists of metal.